Power management circuit and mobile terminal

ABSTRACT

The present disclosure relates to a power management circuit and a mobile terminal having a first switch for blocking current. The first switch blocks an input of an external power supply in a case that a predetermined load operates in a large current/voltage mode. A bi-directional DC converter boosts a battery voltage and supplies it to the load. Thus, the circuit is simplified and the number of components is reduced for power management.

CLAIM OF PRIORITY

This application claims priority to Chinese Application No.201410733941.6, filed on Dec. 4, 2014 (published as CN 104467411 A),which is hereby incorporated by reference.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to the field of power electronics, andmore particularly, to a power management circuit and a mobile terminal.

Description of the Related Art

More and more electronic devices and functionalities are added in amobile terminal, which means that the mobile terminal drives manydifferent types of loads, with challenges in power management. The powermanagement circuit should firstly charge a rechargeable battery, such asa lithium battery, secondly supply electric energy to a system part ofthe mobile terminal, and finally supply electric energy to an externalload which is electrically coupled to the mobile terminal as a load inan OTG mode or in a On The Go mode. Further, the power managementcircuit may need to supply a large voltage or current to some loads,such as LED loads, in some modes.

A conventional power management circuit needs several power stages tooperate together for the above functionalities, and has a complexcircuit configuration. When the power management circuit is formed as anintegrated circuit, it will have a large footprint and be costly.

BRIEF DESCRIPTION OF THE DISCLOSURE

In view of this, the present disclosure provides a power managementcircuit and a mobile terminal, which simplifies a circuit structure forsupplying a relatively large voltage or current to some loads such asLED loads in some modes while reducing the number of components.

According to a first aspect, there is provided a power managementcircuit comprising:

a bi-directional DC converter comprising a low-voltage terminal, a firsthigh-voltage terminal and a second high-voltage terminal, for convertinga first voltage at the first high-voltage terminal into a second voltageand supply the second voltage at the low-voltage terminal in a buckmode, or for converting the second voltage at the low-voltage terminalinto the first voltage and supply the first voltage at the firsthigh-voltage terminal in a first boost mode, or for converting thesecond voltage at the low-voltage terminal into a third voltage andsupply the third voltage at the second high-voltage terminal in a secondboost mode;

a supply terminal for being electrically coupled to an external powersupply or a first load;

a load terminal for being electrically coupled to a second load;

a capacitor being electrically coupled between the load terminal and aground terminal;

a first switch being electrically coupled between the supply terminaland the first high-voltage terminal, and configured to be turned off ina case that the second load operates in the first mode and the supplyterminal is electrically coupled to the external power supply,

wherein the power management circuit is configured to electricallycouple the second high-voltage terminal to the load terminal and outputelectric energy to the load terminal by controlling the bi-directionalDC converter to operate in the second boost mode, in a case that thesecond load operates in the first mode.

Here, the first load may be a predetermined load, such as an LED load,and the second load is an external load.

Preferably, the bi-directional DC converter operates in the second boostmode in a case that the second load operates in the first mode or in asecond mode, in the first boost mode in a case that the supply terminalis electrically coupled to the first load, and in the buck mode in acase that the supply terminal is electrically coupled to the externalpower supply and the second load is inactive,

the first switch is turned off in a case that the second load is active.

Preferably, the bi-directional DC converter comprises:

a second switch electrically coupled between the first high-voltageterminal and an intermediate terminal;

a third switch electrically coupled between the intermediate terminaland ground;

a fourth switch electrically coupled between the intermediate terminaland the second high-voltage terminal;

an inductor electrically coupled between the intermediate terminal andthe low-voltage terminal,

wherein the third switch and the fourth switch are operatively turned onand off to supply the third voltage at the second high-voltage terminal,in a case that the second load operates in the first mode or in thesecond mode,

the third switch and the second switch are turned on and off to supplythe first voltage at the first high-voltage terminal, in a case that thesupply terminal is electrically coupled to the first load, and

the second switch and the third switch are operatively turned on and offto supply the second voltage at the low-voltage terminal, in a case thatsupply terminal is electrically coupled to the external power supply andthe second load is inactive.

According to a second aspect, there is provided a power managementcircuit, comprising:

a bi-directional DC converter comprising a low-voltage terminal, and ahigh-voltage terminal, and configured to convert a first voltage at thehigh-voltage terminal into a second voltage and supply the secondvoltage at the low-voltage terminal in a buck mode, or to convert thesecond voltage at the low-voltage terminal into the first voltage andsupply the first voltage at the high-voltage terminal in a boost mode;

a supply terminal for being electrically coupled to an external powersupply or a first load;

a load terminal for being electrically coupled to a second load;

a capacitor being electrically coupled between the load terminal and aground terminal;

a first switch being electrically coupled between the supply terminaland the high-voltage terminal, and configured to be turned off in a casethat the second load operates in the first mode and the supply terminalis electrically coupled to the external power supply,

wherein the power management circuit is configured to electricallycouple the high-voltage terminal to the load terminal and outputelectric energy to the load terminal by controlling the bi-directionalDC converter to operate in the boost mode, in a case that the secondload operates in the first mode.

Preferably, the bi-directional DC converter comprises a second switchelectrically coupled between the high-voltage terminal and anintermediate terminal;

a third switch electrically coupled between the intermediate terminaland ground;

an inductor electrically coupled between the intermediate terminal andthe low-voltage terminal,

wherein the bi-directional DC converter operates in the boost mode, in acase that the second load operates in the first mode and the supplyterminal is not electrically coupled to the external power supply,and/or in a case that the supply terminal is electrically coupled to thefirst load,

the bi-directional DC converter operates in the buck mode, in a casethat the second load operates in a second mode, or in a case that thesupply terminal is electrically coupled to the external power supply andthe second load is inactive.

Preferably, the power management circuit further comprises:

a battery terminal for being electrically coupled to a rechargeablebattery;

a charge switch being electrically coupled between the low-voltageterminal and the batter terminal;

a fifth switch being electrically coupled between the battery terminaland the load terminal, and configured to be turned on in a case that thesecond load operates in the second mode and the supply terminal is notelectrically coupled to the external power supply or the first load.

Preferably, the bi-directional DC converter comprises:

a second switch electrically coupled between the high-voltage terminaland an intermediate terminal;

a third switch electrically coupled between the intermediate terminaland ground;

an inductor electrically coupled between the intermediate terminal andthe low-voltage terminal,

wherein the bi-directional DC converter operates in the boost mode, in acase that the second load operates in the first mode, or in a case thatthe second load operates in the second mode and the supply terminal isnot electrically coupled to the external power supply, or in a case thatthe supply terminal is electrically coupled to the first load, and

the bi-directional DC converter operates in the buck mode, in a casethat the second load operates in the second mode and the supply terminalis electrically coupled to the external power supply.

Preferably, the power management circuit further comprises:

a sixth switch being electrically coupled between the low-voltageterminal and the load terminal, and configured to be turned on in a casethat the supply terminal is electrically coupled to the external powersupply and the second load operates in the second mode;

a seventh switch being electrically coupled between the high-voltageterminal and the load terminal, and configured to be turned on in a casethat the second load operates in the first mode, or in a case that thesecond load operates in the second mode and the supply terminal is notelectrically coupled to the external power supply.

Preferably, the power management circuit further comprises:

a battery terminal for being electrically coupled to a rechargeablebattery;

a charge switch being electrically coupled between the low-voltageterminal and the batter terminal.

According to a third aspect, there is provided a mobile terminal,comprising:

a rechargeable battery;

a second load;

the above-mentioned power management circuit.

The power management circuit has a first switch for blocking current.The first switch blocks an input of an external power supply in a casethat a predetermined load operates in a large current/voltage mode. Abi-directional DC converter boosts a battery voltage and supplies it tothe load. Thus, the circuit is simplified and the number of componentsis reduced for power management.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentdisclosure will become more fully understood from the detaileddescription given herein below in connection with the appended drawings,and wherein:

FIG. 1 is a schematic circuit diagram of an example power managementcircuit according to the prior art;

FIG. 2 is a schematic circuit diagram of an example power managementcircuit according to a first embodiment of the present disclosure;

FIG. 3 is a schematic circuit diagram of an example power managementcircuit according to a second embodiment of the present disclosure; and

FIG. 4 is a schematic circuit diagram of an example power managementcircuit according to a third embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

Reference will now be made in detail to particular embodiments of thedisclosure, it will be understood that the scope of the presentinvention is not limited to these embodiments. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be readilyapparent to one skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, processes, components, and circuits have not beendescribed in detail so as not to unnecessarily obscure aspects of thepresent

Furthermore, it will be understood by one skilled in the art thatattached drawings are to be regard as illustrative, and may not be drawnto scale.

Also, it will be understood in the following description that the term“circuit” refers to a conductive loop consisting of at least onecomponent or sub-circuit which are electrically coupled orelectromagnetically coupled. When one component/circuit is referred toas being “connected to” another component, or one component/circuit isreferred to as being “connected between” two nodes, it can be connectedwith or coupled to another component directly or with an intermediatecomponent therebetween. The connection of two components can be physicalor logical connection, or physical and logical connection. On thecontrary, when one component is referred to as being “coupled directlyto” or “connected directly to” another component, there will be no anintermediate component between two components.

Where the term “comprising” or “including” is used in the presentdescription and claims, it does not exclude other elements or steps,unless something otherwise is specifically stated. That is, it means“including, but not limited to”.

In the following description that the terms such as “first”, “second”and the like are used herein for purposes of description and are notintended to indicate or imply relative importance or significance. Theterm “plurality”, as being used herein, is defined as two or more thantwo, unless something otherwise is specifically stated.

In some embodiments of the present disclosure, the description is madewith a mobile terminal or an LED load in an electric equipment as anexample of a load which operates in a large voltage/current mode.Nevertheless, these embodiments also apply for other types of loads.

An LED load of a mobile terminal typically operates in two differentmodes, including a flashlight mode (also referred to as a “first mode”)and a torch mode (also referred as to a “second mode”). In theflashlight mode, the LED load flashes in a short time period and needsto be supplied with a large current or voltage in the short time period.In the torch mode, the LED load emits light continuously and needs to besupplied either with a large current or voltage, or with a small currentor voltage.

FIG. 1 is a schematic circuit diagram of an example power managementcircuit according to the prior art. Referring to FIG. 1, the powermanagement circuit 10 includes a first DC converter 11 and a second DCconverter 12 which are connected in series with each other. The first DCconverter 11 has a buck-type topology or a bi-directional topology, andthe second DC converter 12 has a boost-type topology. In a case that asupply terminal IN is connected with an external power supply, the firstDC converter 11 bucks a voltage of the external power supply andsupplies it to a battery 13 for charging. Meanwhile, the second DCconverter 12 boosts the bucked voltage for driving the LED load. In acase that the supply terminal IN is not connected with the externalpower supply, the first DC converter 11 is inactive. Meanwhile, thesecond DC converter 12 boosts a battery voltage for driving the LEDload. Two DC converters are used, including many components. Especially,two inductors are used, which increases a size of the circuit.

FIG. 2 is a schematic circuit diagram of an example power managementcircuit according to a first embodiment of the present disclosure.Referring to FIG. 2, the power management circuit 20 includes abi-directional DC converter 21, a supply terminal IN/OTG, a loadterminal OUT, a capacitor C1 and a first switch M1.

The supply terminal IN/OTG is used for being connected with an externalpower supply or an external load, for supplying a supply voltage to thepower management circuit 20, or for supplying a driving voltage from thepower management circuit to the external load.

The load terminal OUT is used for being connected with a predeterminedload. In this embodiment, the predetermined load is an LED load.

The capacitor C1 is connected between the load terminal OUT and ground,for filtering an output voltage.

The bi-directional DC converter 21 includes a low-voltage terminal SYS,a first high-voltage terminal BUS and a second high-voltage terminalSEC. The bi-directional DC converter 21 performs bi-directional DCconversion. That is, the bi-directional DC converter 21 converts a firstvoltage at the first high-voltage terminal BUS into a second voltage andsupply the second voltage at the low-voltage terminal SYS in a buckmode, or converts the second voltage at the low-voltage terminal SYSinto the first voltage and supply the first voltage at the firsthigh-voltage terminal BUS in a first boost mode, or to convert thesecond voltage at the low-voltage terminal SYS into a third voltage andsupply the third voltage at the second high-voltage terminal SEC in asecond boost mode.

Both the first voltage and the third voltage are larger than the secondvoltage. The first voltage and the third voltage may be determined inaccordance with the external load and the LED load.

The first switch M1 is connected between the first high-voltage terminalBUS and the supply terminal IN/OTG. The second high-voltage terminal SECis connected directly with the load terminal OUT. Accordingly, the firsthigh-voltage terminal BUS may be used for receiving an input voltagefrom the external power supply or providing an output voltage, forsupplying electric energy to the external load.

In this embodiment, the first switch M1 is connected with thehigh-voltage terminal BUS and should have a large breakdown voltage.

In this embodiment, the bi-directional DC converter 21 may be aswitching-type converter as shown in FIG. 2. The bi-directional DCconverter 21 includes a second switch M2, a third switch M3, a fourthswitch M4 and an inductor L. The second switch M2 is connected betweenthe first high-voltage terminal BUS and an intermediate terminal LX. Thethird switch M3 is connected between the intermediate terminal LX andground. The fourth switch M4 is connected between the intermediateterminal LX and the second high-voltage terminal SEC. The inductor L isconnected between the intermediate terminal LX and the low-voltageterminal SYS.

When a supply voltage from the external power supply is detected at thesupply terminal IN/OTG, it is determined that the supply terminal IN/OTGis connected with the external power supply. The first switch M1 isturned on so that the supply voltage at the supply terminal istransferred to the first high-voltage terminal BUS through the firstswitch M1. The second switch M2 and the third switch M3 are operativelyturned on and off so that the bi-directional DC converter 21 bucks thevoltage at the first high-voltage terminal BUS and supplies it to thelow-voltage terminal SYS. The voltage at the low-voltage terminal SYS isused for charging the battery and supplying electric energy to themobile terminal. The bi-directional DC converter 21 operates in a buckmode, in which the second switch M2 is a main power switch and the thirdswitch M3 is a synchronous rectifying switch.

When the external load is detected to be connected with the supplyterminal, the first switch M1 is turned on so that the voltage at thefirst high-voltage terminal BUS is transferred to the supply terminalIN/OTG. The third switch M3 and the second switch M2 are operativelyturned on and off so that the bi-directional DC converter 21 receives abattery voltage at the low-voltage terminal SYS, and boosts and suppliesit to the first high-voltage terminal BUS for supplying electric energyto the external load. The bi-directional DC converter 21 now has a boosttopology, in which the third switch M3 is a main power switch and thesecond switch M2 is a synchronous rectifying switch.

When the LED load is active, the bi-directional DC converter 21 in thisembodiment boosts the battery voltage to a third voltage having a largervalue for driving the LED load, no matter whether the LED load operatesin a flashlight mode (i.e. a first mode), or in a torch mode (i.e. asecond mode). In such case, the first switch M1 is turned off to stopcharging or supplying electric energy. The third switch M3 and thefourth switch M4 are operatively turned on and off so that thebi-directional DC converter 21 receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it to the secondhigh-voltage terminal SEC. The second high-voltage terminal SEC isdirectly connected with the load terminal OUT. Thus, the boosted voltageis directly transferred to the LED load for driving the LED load.

In this embodiment, the bi-directional DC converter 21 operates in aconstant voltage mode. Adjustment transistors Mt1 and Mt2 are connectedin series with LED strings, respectively. The adjustment transistors Mt1and Mt2 operate in a linear mode for supplying a constant drivingcurrent, as required by the LED load.

In this embodiment, the power management circuit 20 further includes abattery terminal BAT and a charge switch Mc. The battery terminal BAT isused for being connected with a rechargeable battery, such as a lithiumbattery. The charge switch Mc is connected between the battery terminalBAT and the low-voltage terminal SYS, for controlling a charging currentof the battery. The charge switch Mc may operate in a linear mode, formaintaining a relatively small charging current. Further, the chargeswitch Mc may be completely turned on when charging or discharging witha large current, and be completely turned off after charging anddischarging. The charge switch Mc needs to block a charging current or adischarging current in two opposite directions. Twometal-oxide-semiconductor field effect transistors (MOSFETs) may beconnected in series and with their sources being adjacent to each other.Thus, the two MOSFETs will be turned on or off simultaneously. It shouldbe understood by one skilled person that the charge switch Mc may beomitted in some cases, and the battery terminal BAT and the low-voltageterminal SYS may be formed as the same one terminal.

In this embodiment, the bi-directional DC converter 21 further includesa capacitor C2 which is connected between the low-voltage terminal SYSand ground, for filtering the output voltage.

The power management circuit according to this embodiment includes afirst switch for blocking current, which blocks an input of the externalpower supply in a case that the LED load operates in a flashlight mode.Moreover, a bi-directional DC converter having two high-voltageterminals is used for boosting a battery voltage and supplying it to theLED load. In a case that the LED load is inactive, the bi-directional DCconverter operates to charge the battery by the external power supply,or to supply electric energy to the load. Thus, a single bi-directionalDC converter can fulfill the requirements of power management, whichsimplifies the circuit structure and reduces the number of components.

FIG. 3 is a schematic circuit diagram of an example power managementcircuit according to a second embodiment of the present disclosure.Referring to FIG. 3, the power management circuit 30 includes abi-directional DC converter 31, a supply terminal IN/OTG, a loadterminal OUT, a capacitor C1 and a first switch M1.

The supply terminal IN/OTG is used for being connected with an externalpower supply or an external load, for supplying a supply voltage to thepower management circuit 30, or for supplying a driving voltage from thepower management circuit to the external load.

The load terminal OUT is used for being connected with a predeterminedload. In this embodiment, the predetermined load is an LED load.

The capacitor C1 is connected between the load terminal OUT and ground,for filtering an output voltage.

The bi-directional DC converter 31 includes a low-voltage terminal SYS,and a high-voltage terminal BUS. The bi-directional DC converter 31converts a first voltage at the high-voltage terminal BUS into a secondvoltage and supply the second voltage at the low-voltage terminal SYS,or converts the second voltage at the low-voltage terminal SYS into thefirst voltage and supply the first voltage at the high-voltage terminalBUS. The first voltage is larger than the second voltage.

The first switch M1 is connected between the high-voltage terminal BUSand the supply terminal IN/OTG.

The high-voltage terminal BUS is connected with the first switch M1 andis coupled to the load terminal OUT. In this embodiment, thehigh-voltage terminal BUS is connected directly with the load terminalOUT.

In this embodiment, the bi-directional DC converter 31 may be aswitching-type converter as shown in FIG. 3. The bi-directional DCconverter 31 includes a second switch M2, a third switch M3, a fourthand an inductor L. The second switch M2 is connected between thehigh-voltage terminal BUS and an intermediate terminal LX. The thirdswitch M3 is connected between the intermediate terminal LX and ground.The inductor L is connected between the intermediate terminal LX and thelow-voltage terminal SYS.

The bi-directional DC converter 31 converts the first voltage at thehigh-voltage terminal BUS into the second voltage and supplies it to thelow-voltage terminal SYS, by operatively turning on and off the secondswitch M2 and the third switch M3. The bi-directional DC converter 31operates in a buck mode, in which the second switch M2 is a main powerswitch and the third switch M3 is a synchronous rectifying switch.

The bi-directional DC converter 31 also converts the second voltage atthe low-voltage terminal SYS into the first voltage and supplies it tothe high-voltage terminal BUS, by operatively turning on and off thethird switch M3 and the second switch M2. The bi-directional DCconverter 31 operates in a boost mode, in which the third switch M3 is amain power switch and the second switch M2 is a synchronous rectifyingswitch.

In this embodiment, the power management circuit 30 further includes abattery terminal BAT and a charge switch Mc. The battery terminal BAT isused for being connected with a rechargeable battery. The charge switchMc is connected between the battery terminal BAT and the low-voltageterminal SYS, for controlling a charging current of the battery. Thecharge switch Mc may operate in a linear mode, for maintaining arelatively small charging current. Further, the charge switch Mc may becompletely turned on when charging or discharging with a large current,and be completely turned off after charging and discharging. Moreover,the power management circuit 30 may also include a fifth switch M5. Thefifth switch M5 is connected between the battery terminal BAT and theload terminal OUT, and is turned on in a case that the LED load operatesin the second mode and the supply terminal IN/OTG is not connected withthe external power supply or the external load, for receiving thebattery voltage for driving the LED load.

When a supply voltage from the external power supply is detected at thesupply terminal IN/OTG, the first switch M1 is turned on so that thesupply voltage at the supply terminal is transferred to the high-voltageterminal BUS through the first switch M1. The bi-directional DCconverter 31 operates in a buck mode for bucking a voltage at thehigh-voltage terminal BUS and supplying it to the low-voltage terminalSYS. The voltage at the low-voltage terminal SYS is used for chargingthe battery and supplying electric energy to other parts of the system.In a case that the LED load operates in a flashlight mode, the voltageat the high-voltage terminal BUS, which has a larger value, is useddirectly for driving the LED load to emit light continuously. In a casethat the LED load operates in a flashlight mode, the first switch M1 isturned off for blocking an input of the external power supply. Thebi-directional DC converter 31 operates in a boost mode, in which thebi-directional DC converter 31 receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it at the high-voltageterminal BUS. The boosted voltage is further transferred to the loadterminal OUT for driving the LED load. Thus, the LED load may operatewith a higher voltage as a driving voltage.

When the external load is detected to be connected with the supplyterminal, the first switch M1 is turned on so that the voltage at thehigh-voltage terminal BUS is transferred to the supply terminal IN/OTG.The bi-directional DC converter 31 receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it to the high-voltageterminal BUS for supplying electric energy to the external load.

In a case that the supply terminal is not connected with an externaldevice, and the LED load operates in a flashlight mode, thebi-directional DC converter 31 receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it to the high-voltageterminal BUS for supplying electric energy to the LED load. In a casethat the LED load operates in a torch mode, the fifth switch M5 isturned on and the battery voltage is directly used for driving the LEDload.

In this embodiment, the bi-directional DC converter 21 further includesa capacitor C2 which is connected between the low-voltage terminal andground, for filtering the output voltage.

The power management circuit according to this embodiment includes afirst switch for blocking current, which blocks an input of the externalpower supply in a case that the LED load operates in a flashlight mode.Moreover, a bi-directional DC converter having one high-voltage terminalis used for boosting a battery voltage and supplying it to the LED load.In a case that the LED load is inactive, the bi-directional DC converteroperates to charge the battery by the external power supply, or tosupply electric energy to the load. Thus, a single bi-directional DCconverter can fulfill the requirements of power management, whichsimplifies the circuit structure and reduces the number of components.

FIG. 4 is a schematic circuit diagram of an example power managementcircuit according to a third embodiment of the present disclosure.Referring to FIG. 4, the power management circuit 40 includes abi-directional DC converter 41, a supply terminal IN/OTG, a loadterminal OUT, a capacitor C1 and a first switch M1.

The supply terminal IN/OTG is used for being connected with an externalpower supply or an external load, for supplying a supply voltage to thepower management circuit 40, or for supplying a driving voltage from thepower management circuit 40 to the external load.

The load terminal OUT is used for being connected with a predeterminedload. In this embodiment, the predetermined load is an LED load.

The capacitor C1 is connected between the load terminal OUT and ground,for filtering an output voltage.

The bi-directional DC converter 41 includes a low-voltage terminal SYS,and a high-voltage terminal BUS. The bi-directional DC converter 41converts a first voltage at the high-voltage terminal BUS into a secondvoltage and supply the second voltage at the low-voltage terminal SYS,or converts the second voltage at the low-voltage terminal SYS into thefirst voltage and supply the first voltage at the high-voltage terminalBUS. The first voltage is larger than the second voltage.

The first switch M1 is connected between the high-voltage terminal BUSand the supply terminal IN/OTG.

The high-voltage terminal BUS is connected with the first switch M1 andis coupled to the load terminal OUT. In this embodiment, thehigh-voltage terminal BUS is connected with the load terminal OUTthrough a seventh switch M7. That is, the seventh switch M7 is connectedbetween the high-voltage terminal BUS and the load terminal OUT.

In this embodiment, the bi-directional DC converter 41 may be aswitching-type converter as shown in FIG. 4. The bi-directional DCconverter 41 includes a second switch M2, a third switch M3, a fourthand an inductor L. The second switch M2 is connected between thehigh-voltage terminal BUS and an intermediate terminal LX. The thirdswitch M3 is connected between the intermediate terminal LX and ground.The inductor L is connected between the intermediate terminal LX and thelow-voltage terminal SYS.

The bi-directional DC converter 41 converts the first voltage at thehigh-voltage terminal BUS into the second voltage and supplies it to thelow-voltage terminal SYS, by operatively turning on and off the secondswitch M2 and the third switch M3. The bi-directional DC converter 41operates in a buck mode, in which the second switch M2 is a main powerswitch and the third switch M3 is a synchronous rectifying switch.

The bi-directional DC converter 41 also converts the second voltage atthe low-voltage terminal SYS into the first voltage and supplies it tothe high-voltage terminal BUS, by operatively turning on and off thethird switch M3 and the second switch M2. The bi-directional DCconverter 41 operates in a boost mode, in which the third switch M3 is amain power switch and the second switch M2 is a synchronous rectifyingswitch.

In this embodiment, the power management circuit 40 further includes asixth switch M6 which is connected between the low-voltage terminal SYSand the load terminal OUT.

When a supply voltage from the external power supply is detected at thesupply terminal IN/OTG, the first switch M1 is turned on so that thesupply voltage at the supply terminal is transferred to the high-voltageterminal BUS through the first switch M1. The bi-directional DCconverter 41 operates in a buck mode for bucking a voltage at thehigh-voltage terminal BUS and supplying it to the low-voltage terminalSYS. The voltage at the low-voltage terminal SYS is used for chargingthe battery and supplying electric energy to other parts of the system.The voltage at the low-voltage terminal SYS is a stable and buckedvoltage supplied from the converter. In a case that the LED loadoperates in a torch mode, the sixth switch M6 is turned on and theseventh transistor M7 is turned off, and the voltage at the low-voltageterminal SYS, which has a smaller value, is used for driving the LEDload to emit light continuously. In a case that the LED load operates ina flashlight mode, the first switch M1 is temporarily turned off. Thebi-directional DC converter 41 receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it at the high-voltageterminal BUS. The bi-directional DC converter 41 supplies a voltagehaving a larger value for driving the LED load.

When the external load is detected to be connected with the supplyterminal, the first switch M1 is turned on so that the voltage at thehigh-voltage terminal BUS is transferred to the supply terminal IN/OTG.The bi-directional DC converter 31 receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it to the high-voltageterminal BUS for supplying electric energy to the external load. In suchcase, the voltage at the low-voltage terminal is the battery voltage,which is unstable. The sixth switch M6 is turned off and the seventhswitch M7 is turned on, for supplying a voltage having a larger value atthe high-voltage terminal BUS for driving the LED load, no matterwhether the LED load operates in a flashlight mode or in a torch mode.

In a case that the supply terminal is not connected with an externaldevice, the bi-directional DC converter 41 operates in a boost mode, inwhich the bi-directional DC converter receives a battery voltage at thelow-voltage terminal SYS, and boosts and supplies it to the high-voltageterminal BUS, no matter whether the LED load operates in a flashlightmode or in a torch mode. The sixth switch M6 is turned off and theseventh switch M7 is turned on, for supplying the voltage at thehigh-voltage terminal BUS to the LED load. It avoids an unstable drivingvoltage of the LED load when electric energy is supplied directly fromthe battery.

Preferably, the power management circuit 40 according to this embodimentfurther includes a battery terminal BAT and a charge switch Mc. Thebattery terminal BAT is used for being connected with a rechargeablebattery. The charge switch Mc is connected between the battery terminalBAT and the low-voltage terminal SYS, for controlling a charging currentof the battery. The charge switch Mc may operate in a linear mode, formaintaining a relatively small charging current. Further, the chargeswitch Mc may be completely turned on when charging or discharging witha large current, and be completely turned off after charging anddischarging.

The power management circuit according to this embodiment includes afirst switch for blocking current, which blocks an input of the externalpower supply in a case that the LED load operates in a flashlight mode.Moreover, a bi-directional DC converter having one high-voltage terminalis used for boosting a battery voltage and supplying it to the LED load.In a case that the LED load is inactive, the bi-directional DC converteroperates to charge the battery by the external power supply, or tosupply electric energy to the load. Thus, a single bi-directional DCconverter can fulfill the requirements of power management, whichsimplifies the circuit structure and reduces the number of components.

The foregoing descriptions of specific embodiments of the presentinvention have been presented, but are not intended to limit theinvention to the precise forms disclosed. It will be readily apparent toone skilled in the art that many modifications and changes may be madein the present invention. Any modifications, equivalence, variations ofthe preferred embodiments can be made without departing from thedoctrine and spirit of the present invention.

1.-12. (canceled)
 13. A power management circuit, comprising: abi-directional DC converter comprising a common inductor coupled betweena supply terminal and a rechargeable battery; a second load having firstand second modes of operation, wherein said second load is coupled tosaid bi-directional DC converter in a predetermined arrangement suchthat when in said first mode, a stable voltage is provided to saidsecond load; wherein when said supply terminal is configured to receivean external power supply, said bi-directional DC converter is controlledto operate in a buck mode to charge said rechargeable battery; andwherein when said supply terminal is configured to receive a first load,said bi-directional DC converter is controlled to operate in a boostmode to discharge said rechargeable battery to drive said first load.14. The power management circuit according to claim 13, wherein saidbi-directional DC converter comprises: second and third switches coupledin series between said supply terminal and ground; a fourth switchelectrically coupled between an intermediate common terminal betweensaid second and third switches and said second load; and said inductorelectrically coupled between said common terminal between said secondand third switches and said bi-directional battery, wherein when saidsecond load is in said first mode and said external power supply isprovided at said supply terminal, said external power supply is cut offand said bi-directional DC converter is in a boost mode that configuressaid rechargeable battery as a supply voltage to provide said stablevoltage to said second load.
 15. The power management circuit accordingto claim 14, wherein said second load is driven by said bi-directionalDC converter that configures said rechargeable battery as a supplyvoltage when said second load is in said second mode.
 16. The powermanagement circuit according to claim 13, further comprising a chargeswitch electrically coupled between said bi-directional DC converter andsaid rechargeable battery, and being configured to control a chargingcurrent and a discharging current of said rechargeable battery.
 17. Thepower management circuit according to claim 13, further comprising afirst switch electrically coupled between said supply terminal and saidbi-directional DC converter, wherein said first switch is turned offwhen said second load operates in said first mode and said supplyterminal is electrically coupled to said external power supply.
 18. Thepower management circuit according to claim 13, wherein saidbi-directional DC converter comprises: second and third switches coupledin series between said supply terminal and ground; and said inductorelectrically coupled between an intermediate common terminal betweensaid second and third switches and said rechargeable battery; whereinsaid second load is coupled to said rechargeable battery and a commonterminal between said supply terminal and said second switch.
 19. Thepower management circuit according to claim 18, wherein: when saidrechargeable battery is charged and said second load is in said firstmode, said second load is provided said stable voltage by saidrechargeable battery directly through a first controllable switch; andwhen said rechargeable battery is discharged and said second load is insaid first mode, said second load is provided said stable voltage bysaid bi-directional DC converter operated in a boost mode thatconfigures said rechargeable battery as a supply voltage.
 20. The powermanagement circuit according to claim 18, further comprising a fifthswitch electrically coupled between said rechargeable battery and saidsecond load.
 21. The power management circuit according to claim 18,further comprising a sixth switch electrically coupled between a commonterminal between said second switch and said supply terminal, and saidsecond load.
 22. The power management circuit according to claim 18,wherein said second load is driven by said external power supply whensaid second load is in said second mode and said external power supplyis provided at said supply terminal.
 23. The power management circuitaccording to claim 18, wherein said second load is driven by saidrechargeable battery when said second load is in said second mode. 24.The power management circuit according to claim 18, wherein said secondload is driven by said bi-directional DC converter in a boost mode whensaid second load is in said second mode.
 25. The power managementcircuit according to claim 18, wherein when said second load is in saidfirst mode, said second load is provided said stable voltage by saidbi-directional DC converter that is operated in a boost mode thatconfigures said rechargeable battery as a supply voltage.